The invention relates to new fruit pomace compositions and methods of using these compositions, e.g., for plant pathogen control and bioremediation.
Pomace is the solid waste presscake left behind after fruit processing. It is difficult to dispose of because its high water content prevents it from composting well. Further, pomace also has a low pH, and high carbohydrate and low protein content, limiting its usefulness as an animal feed. Over one million metric tons of apple pomace alone are produced each year in the United States, and disposal fees are estimated to exceed $10 million. The grape industry produces nearly five million tons of grapes each year, over 40% of which is used for processing purposes. Pomace accounts for as much as 20% of the wet weight of the fruit, and annual production of pomace is over 400,000 tons per year.
Fruit pomace has been used as a raw material to produce certain commercial products, such as ethanol, acetic acid, citric acid, and some dyes and colorants. Pomace has also been inoculated with fungi, such as Trichoderma reesei, Saccharomyces lipolytica, and others, as a means to increase the protein content in the pomace, and increase its value as a cattle feed. Edible mushrooms such as shiitake and oyster mushrooms have also been grown on a pomace substrate, but there is still far more pomace produced than can be used in these ways.
Trichoderma is a fungus known to parasitize a number of other soil-borne fungi that are pathogenic to plants. Much research has been done to determine ways to exploit this natural inhibition of plant pathogens. Few practical applications have resulted, however, mostly because the beneficial fungi are out-competed by other native fungi under typical field conditions.
Many other organisms have been shown to parasitize plant pathogens, including Pythium nunn, which attacks P. ultimum (damping-off of cucumber), Rhizoctonia solani (root rot), and Phytophthora parasitica (buckeye rot of tomato). Talaromyces flavus is particularly aggressive, and suppresses R. solani root rot, Sclerotinia sclerotiorum wilt of sunflowers, and Verticillium spp., which causes devastating wilts in a wide variety of crops. Experiments also have been done using Sporidesmium sclerotivorum against Sclerotinia minor, which causes lettuce drop, but current methods of culturing Sporidesmium have proved uneconomical for field use. Several fungi, including Teratosperma oligocladum, Suillus granulatus, Peniophora spp., and Pisolithus tinctorius are thought to have potential uses in forestry applications, in preventing root rot in pine species from Rhizoctonia spp. and Phytophthora spp.
Bioremediation is the use of organisms to remove pollutants from the environment. Several naturally-occurring microorganisms exist that degrade organic pollutants, such as Phanerochaete chrysosporium strain BKM-F-1767, Trametes spp., and Bjerkandera adusta. These three fungi are known to degrade polycyclic hydrocarbons, including fluorene and benzoa! pyrene, and have potential use in bioremediation of contaminated soil. Strains of Pseudomonas spp., Alcaligenes, spp., Acinetobacter spp., and Marinobacter hydrocarbonoclasticus have been found growing in petroleum-contaminated marine sediments, and could be used to clean up oil spills. In the field, however, additives must usually be applied to the substrate to promote the growth of these microorganisms. Oleophilic fertilizers are often used, because the nutrients dissolve into the oil and also allow microbial growth at the oil-water boundary (LaCotte, et al., 1995, Chemosphere 31:4351).